In the past, designers of avionics navigation systems have endeavored to provide systems with improved abilities to more precisely make location determinations using GPS satellites. One widely accepted approach to enhancing positional resolution for GPS receivers has been the use of differential GPS, which involves using a GPS receiver located at a known fixed location to generate pseudo range correction data, which then is provided to mobile receivers via a data link connection, where it is used to enhance the position determination abilities of the mobile receiver. This method is used widely in commercial airports throughout the world. When DGPS is used for commercial air carriers, it becomes necessary to have a very precise and robust DGPS system. A simple DGPS system provides much enhanced ability to determine position; however, the pseudo range computations made by a single DGPS receiver are not perfect. Numerous sources of errors still exist. Consequently, many airports are using an averaging technique to further reduce the errors present in a single DGPS receiver approach. These airports will place several DGPS receivers, each at a different surveyed location around the airfield, and calculate pseudo range correction data for each location. It is widely believed that many of the errors will be cancelled out and that an average of several, 5 or more, of the pseudo range corrections will be more precise than any single data set.
Another approach that has been used in the past has been to generate pseudo range correction data by a single GPS receiver and a single surveyed antenna.
While these DGPS stations have many advantages, they also have significant drawbacks.
First of all, for the multiple GPS receiver method, the cost of using five or more linked DGPS receivers and the computing equipment used to operate the system, can be very expensive. Secondly, for the multiple GPS receiver method, the position determined from such DGPS stations may have much improved precision. The situation may still exist that the pseudo range correction data sent to the mobile GPS receivers may result in a position determination that fails to meet the necessary precision requirements. For the single GPS receiver and single antenna method, the quality assessment of such a system is very limited, because using the same GPS receiver and the same antenna to confirm quality as to generate the data itself eliminates the ability of detecting errors which are resulting from the receiver and antenna themselves. Consequently, there exists a need for improvement in systems and methods for monitoring and reporting pseudo range correction data.